1. Field of the Invention
The present invention relates to a device and methods for controlling and recording chemical concentrations in a clean-in-place system or similar automated washer.
2. Description of the Related Art
Food processing equipment, such as that found in dairies, breweries, and carbonated beverage plants, typically includes tanks, pumps, valves and fluid piping. This food processing equipment often needs to be cleaned between each lot of product processed through the equipment. However, the tanks, pumps, valves and piping can be difficult to clean because the various components may be difficult to access and disassemble for cleaning. Because of these cleaning difficulties, many food processing plants now use clean-in-place systems in which the tanks, pumps, valves and piping of the food processing equipment remain physically assembled, and various cleaning, disinfecting and rinsing solutions are circulated by the clean-in-place system through the food processing equipment to effect the cleaning process.
An example clean-in-place cleaning cycle normally begins with a pre-rinse cycle wherein water is pumped through the food processing equipment for the purpose of removing loose soil in the system. Typically, an alkaline wash would then be recirculated through the food processing equipment. This alkaline wash would chemically react with the soils of the food processing equipment to further remove soil. A third step would again rinse the food processing equipment with water, prior to a fourth step wherein an acid rinse would be circulated through the batch processing system. The acid rinse would neutralize and remove residual alkaline cleaner and remove any mineral deposits left by the water. Finally, a post-rinse cycle would be performed, typically using water and/or a sanitizing rinse. Such clean-in-place systems (and associated cleaning compositions) are known in the art, and examples can be found in U.S. Pat. Nos. 6,423,675, 6,391,122, 6,161,558, 6,136,362, 6,089,242, 6,071,356, 5,888,311, 5,533,552, 5,427,126, 5,405,452, 5,348,058, 5,282,889, 5,064,561, 5,047,164, 4,836,420, and 2,897,829.
Devices for the automatic dispensing of cleaning, rinsing and/or sanitizing chemicals to the chemical reservoirs of a clean-in-place system or similar automated washer are also known. For example, U.S. Pat. Nos. 5,681,400, 5,556,478 and 5,404,893 describe a programmable detergent controller where a microprocessor compares a detergent concentration set-point with a detergent concentration from a sensor in a wash tank. Based on this comparison, the microprocessor determines when a solenoid valve should be opened to allow the feeding of detergent solution into the wash tank.
U.S. Patent Application No. 2003/0127110 describes an automatic dispensing system for a washer. A probe sensor measures the electrical conductivity of water within the washer and produces a conductivity measurement. Because detergents are an alkali and or an acid, the water conductivity varies with the detergent concentration. Therefore, by sensing the water conductivity, a control system is able to determine how much detergent is needed to be added at the beginning of a wash cycle. The controller operates a detergent flow control device in a first mode in which the quantity of detergent dispensed into the washer is determined in response to the electrical conductivity of the water. If the conductivity measurement is determined to be unreliable, the controller operates in a second mode in which a predefined quantity of detergent is dispensed into the washer. In the second mode, software turns on the detergent pump a fixed period of time required to dispense the predefined quantity of liquid detergent as specified by the software configuration parameters.
U.S. Pat. No. 5,500,050 describes a detergent dispenser controller for use with a washing device that measures detergent concentration in a tank by measuring the conductivity of the detergent solution in the tank. Whenever the detergent dispenser is powered on, it determines the difference between the measured tank detergent concentration and a specified detergent concentration set point value. The computed difference between the set point and the current detergent concentration are used to compute a detergent feed on time. The detergent dispenser is then turned on for the computed feed on time.
U.S. Pat. Nos. 5,494,061 and 5,453,131 describe a liquid chemical dispensing system for dispensing a plurality of liquid chemicals into a washer. The system includes at least a detergent pump and a rinse agent pump, and a data processor enables a user to set values for a rinse run time parameter, a detergent run time parameter, and a rinse delay time, and stores those parameters in the non-volatile memory.
U.S. Pat. No. 4,756,321 describes a chemical dispenser and controller for industrial washers. The level of detergent concentration in the wash water is measured by a conductivity sensor. The controller converts wash water conductivity measurements into detergent concentration measurements. The controller also monitors the detergent concentration level and generates an alarm if the measured detergent concentration fails to increase by at least a predefined amount while the detergent feeding mechanism is turned on. Another feature of the controller is that it generates an alarm if the measured detergent concentration fails to reach its target level after the detergent feeding mechanism has been on for a predetermined time period.
The known devices for the automatic dispensing of chemicals to the chemical reservoirs of a clean-in-place system may provide for more efficient use of cleaning chemicals. For instance, the overuse of a cleaning chemical can be avoided by measuring the concentration of a cleaning chemical in a wash tank and only adding enough cleaning chemical to keep the wash tank cleaning solution at a predetermined concentration. However, conductivity probes can by fouled over time by chemical build-up thereby providing false indications of the water conductivity. Also, conductivity probes can fail thereby providing no indication of the water conductivity. Systems with fouled or nonfunctioning probes lead to overuse of a cleaning chemical.
Devices for monitoring clean-in-place system wash conditions are also known. U.S. Pat. No. 6,089,242 describes a dairy pipeline washing system including sensors that monitor wash conditions. An example sensor is a wash water pH sensor. The system includes a data processor that receives signals from the sensors and compares predetermined wash parameters with the sensed wash conditions. The data processor allows a user to adjust parameters. Alarm signals are provided for out of range readings to allow for altering the chemical composition. The system also allows an operator to alter the amount of chemical to be dispensed. Also, in U.S. Patent Application No. 2002/0119574 and U.S. Pat. No. 6,323,033, there is described a clean in place system where multiple conductivity sensors are used to determine if a milk line is sufficiently cleaned with cleaning fluid.
The known devices for monitoring clean-in-place system wash conditions may provide for more efficient operation of a clean-in-place system. However, these devices may not be suitable for diagnosing clean-in-place system fluid flow problems such as leaking valves.
Thus, there is still a need for a device and methods for controlling and recording chemical concentrations in a clean-in-place system in order to avoid the overuse of cleaning chemicals and to provide for a diagnosis of clean-in-place system fluid flow problems.